1. Field of the Invention
The present invention relates to an ultrasound endoscope having a convex-type ultrasound probe in which an observation optical system, a treatment instrument outlet, and a plurality of ultrasound transducers are arranged at a distal end of an insertion portion of an endoscope.
2. Description of the Related Art
As an endoscope for performing ultrasound observation in a body cavity, or therapy and treatment by using treatment instruments, an ultrasound endoscope having a convex-type ultrasound probe at a distal end of the endoscope is known. The convex-type ultrasound probe is configured by arranging a plurality of ultrasound transducers in a convex circular arc shape.
As the ultrasound endoscopes having convex-type ultrasound probes, the ones disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 8-131442 and Japanese Patent Application Laid-Open Publication No. 2004-350700 (see FIG. 19) are cited. In each of the ultrasound endoscopes, an observation optical system is included at a distal end rigid portion in the vicinity of an ultrasound probe, and the observation optical system has an optical axis in a diagonally forward direction.
In an ultrasound endoscope, such positional relationship as to allow observation of an inside of an observation region as an ultrasound tomography image while visually recognizing the observation region with an observation optical system is essential. In order to confirm the insertion depth or the like of a treatment instrument by an ultrasound tomography image, an ultrasound scanning range with an operation range of the treatment instrument taken into consideration is required.
Therefore, in the case of each of the observation optical systems with diagonally forward views as disclosed in Japanese Patent Application Laid-Open Publication No. 8-131442 and Japanese Patent Application Laid-Open Publication No. 2004-350700, the diagonally forward optical axis and the operation range of the treatment instrument can be contained within the ultrasound scanning range by providing an ultrasound probe at a distal end side of the distal end rigid portion.
However, in the ultrasound endoscope disclosed in Japanese Patent Application Laid-Open Publication No. 8-131442, the structure including the ultrasound probe in addition to the distal end rigid portion makes the rigid length of a so-called endoscope insertion portion.
Further, in the structure of the ultrasound endoscope disclosed in Japanese Patent Application Laid-Open Publication No. 2004-350700, a slope is provided at a distal end rigid portion, and an ultrasound probe is loaded on the slope. In this structure, the distal end rigid length is shorter as compared with the ultrasound endoscope disclosed in the Japanese Patent Application Laid-Open Publication No. 8-131442. However, in order to enable to contain the treatment instrument which is led out from a treatment instrument outlet within the ultrasound scanning range, the ultrasound endoscope disclosed in Japanese Patent Application Laid-Open Publication No. 2004-350700 is provided with an ultrasound probe in a semi-circular shape with an ultrasound scanning range at 180 degrees. In the ultrasound endoscope, the structure including the length which is twice as long as the radius of curvature of the ultrasound probe in addition to the distal end rigid portion makes the distal end rigid length.